Method of laminating one or more materials with a base structure for use in a high vacuum electron tube and method of masking the base preparatory to lamination

ABSTRACT

A method of making a structure for use in a black and white or color Kinescope or the like, the structure being called a multichannel array and including a perforated channel type electron multiplier with two perpendicular sets of insulated conductive strips extending over rows and columns of the multiplier holes. The strips have holes in registration with the multiplier holes. Conductive strips and glass insulating layers are deposited using a photoresist layer with or without a transparent photographic film. The photoresist is exposed to light through the multiplier holes.

United States Patent 1 Orthuber METHOD OF LAMINATING ONE OR MOREMATERIALS WITH A BASE STRUCTURE FOR USE IN A HIGH VACUUM ELECTRON TUBEAND METHOD OF MASKING THE BASE PREPARATORY T0 LAMINATION [75] Inventor:Richard Kaspar Orthuber,

Sepulveda, Calif. [73] Assignee: International Telephone and TelegraphCorporation, New York, NY.

[22] Filed: Dec. 2, 1971 [21] Appl. No.: 204,158

[56] References Cited UNITED STATES PATENTS 3,541,254 1111970 Orthuber178/73 [451 Jan. 8, 1974 3,412,456 1l/l968 Ebisawa 96/362 3,567,5083/1971 Cox et al. 96/36.2 3,567,506 3/1971 Belardi 96/362 3,542,55011/1970 Conrad et a] 96/362 Primary ExaminerNorman G. Torchin AssistantExaminer-Edward C. Kimlin Attorney-C. Cornell Remsen, Jr. et a1.

[5 7] ABSTRACT holes. Conductive strips and glass. insulating layers aredeposited using a photoresist layer with or without a transparentphotographic film. The photoresist is exposed to light through themultiplier holes.

7 Claims, 17 Drawing Figures 1 METHOD OF LAMINATING ONE OR MOREMATERIALS WITH A BASE STRUCTURE FOR USE IN A HIGH VACUUM ELECTRON TUBEAND METHOD OF MASKING THE BASE PREPARATORY TO LAMINATION BACKGROUND OFTHE INVENTION This invention relates to the art of fabricatingstructures called multichannel arrays or the like, and moreparticularly, to a method of making perforate laminates.

The present invention may be employed for many purposes not disclosedherein, but has been found especially useful in the fabrication of adevice called a multichannel array (MCA) disclosed in U. S. Pat. No.3,541,254. This device has a multitude of very, very small andintricatecomponent parts. It would thus normally be difficult to make within aresonable time and at reasonable cost.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS In thedrawings which are to be regarded as merely illustrative;

FIG. 1 is a diagrammatic view of a television receiver disclosed inthesaid patent;

FIG. 2 is a perspective view of a structure shown internally of theevacuated envelope of a Kinescope in FIG. 1, the structure being calleda multichannel array (MCA);

FIG. 3 is a broken away sectional view of the MCA taken on the line 3--3shown in FIG..2;

FIG. 4 is a dielectric plate which may be employed with a channel typeelectron multiplier incorporated in the MCA of FIGS. 2 and 3;

FIG. 5 is a sectional view through the plate illustrating steps ofdepositing an electrode on opposite surfaces of the plate shown in FIG.4;

FIG. 6 is a similar sectional view through the structure of FIG. 5 witha transparent photographic film thereon; I

FIG. 7 is a sectional view similar to FIG. 6 with a negative photoresistlayer on the film which has been partially exposed to light; I FIG. 8 isa sectionalview similar to FIG. 7 with portions of the negativephotoresist washed away, and the film area between remaining photoresistlayer portions filled with frit;

FIG. 9 is a sectional view similar to FIG. 8, with the frit glazed andthe film and negative photoresist decomposed in an oven;

FIG. 10 is a sectional view similar to FIG. 7 illustratinganother'method of exposing a photoresist layer;

FIG. 11 is a sectional view illustrating a conductive metal stripevaporating step;

FIG. 12 is a sectional view of a partially constructed MCA having alayer of insulating glass and conductive strips bonded thereto in anoven;

FIG. 13 is a sectional view similar to FIG. 12 illustrating how a secondglass layer is bonded to the laminate shown in FIG. 12;

FIG. 14 is a sectional view similar to FIG. 13 with hardened positivephotoresist strips fixed on top of the assembly;

FIG. 15 is a sectional view of an assembly which may be identical tothat shown in FIGS. 2 and 3; and

FIGS. 16 and 17 are sectional views through laminates illustrating analternative method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagrammatic viewof a television receiver disclosed in the said patent. By this referencehereto, the entire disclosure of the said patent is hereby incorporatedhereat as though fully set forth herein.

As shown in FIG. I, an intensity control circuit is provided at 10. Agating control circuit is provided at 11. Intensity control may beperformed in several ways, as described in the said patent.

Circuit 10 may be identical to the intensity control 100 disclosed inthe said patent, if desired. Circuit 11 may be identical to the scancontrol 101 disclosed in said patent, if desired.

In FIG. 1, a Kinescope is indicated at 12 having an evacuated envelope13, a photocathode 14, a multichannel array 15 and an'aluminizedphosphor screen 16. A lamp 17 is actuable to flood the photocathode 14with light and thereby to supply primary electrons to the multichannelarray (MCA) 15.

MCA 15, as will be explained, may include a channel type electronmultiplier having a multitude of holes therethrough. Two sets ofperpendicular spaced con-' ductive strips are employed to gate outelectrons from only three holes at a time or from only one hole at atime. Thus, gating provides an entirely new concept in what was done inthe prior art to scan an electron beam across a luminescent screen suchas screen 16.

MCA 15 is again shown-in FIG. 2 including a dielectric plate 18sandwiched in between input and output electrodes 19 and 20,respectively.

Glass layers 21 and 22 insulate a plurality of horizontal conductivestrips 23. Aplurality of spaced and insulated conductive strips 24 arefixed to the upper surface of glass layer 22, as shown in FIG. 2. I

As shown in FIG. 3, plate 18 has a plurality of holes 25 extendingcompletely therethrough over much or all of the left hand face thereof,as viewed in FIG. 3. Holes 25 may be quite long, if desired, incomparison to their diameters. Holes 25 may be substantially defined bythe cylindrical internal surfaces of plate 18 These cylindrical internalsurfaces are made secondary emissive at least'by the time envelope 13 issealed.

Electrode 20 has holes 26 which lie in registration with holes 25.Similarly, electrode 19 has holes 27 which lie in registration withholes 25. The same is true, respectively, of holes 28 in layer 2.1,holes 29 in strips 23, holes 30 in layer 22 and holes 31 in strips 24.

A plate 32 is shown in FIG. 4 which may be identical to plate 18.Electrodes 33 and 34 may be evaporated onto plate 32, as shown in FIG.5. Plate 32 may be made of any conventional ceramic employed inconventional channel type electron multipliers including, but notlimited to, leaded glass. Electrodes 33 and 34 may be made of aconductive metal. Electrodes 33 and 34 thus correspond to electrodes 19and 20, respectively, shown in FIG. 3.

A transparent photographic film 35 is then adhered to electrode 33, asshown in FIG. 6.

A negative photoresist layer 36 is then deposited on top of film 35, asshown in FIG. 7. Film 35 is shown only as a line in FIG. 7 because film35 is very thin in comparison to the thickness of layer 36. Further,throughout the drawings hereof, many dimensions have been exaggeratedfor clarity.

In FIG. 7, illumination is provided by a lamp 37 which shines light in adirection indicated by an arrow 38 through hole 39 in plate 32. Asbefore, electrodes 33 and 34 have holes which lie in registration withholes 39. Moreover, film 35 is transparent to the light provided by lamp37. Portions 40 of negative photoresist layer 36 are then exposed to thelight which emanates from a position on the side of plate 32 oppositethe side on which film 35 is positioned. Portions 41 of layer 36 areleft unexposed.

It is inherent in the nature of negative photoresist that only theexposed portions are hardened. Portions 41 are then washed away, andfrit is deposited in the positions of portions 41, as indicated at 42 inFIG. 8.

The assembly of FIG. 8 is then fired in an oven or furnace 43, as shownin FIG. 9. After firing, film 35 and hardened negative photoresistportions 40 are decomposed and effectively removed from the assembly,the firing causing frit 42 to be bonded to electrode 33 at 44 in theposition shown in FIG. 9. Layer 44 is then a substantially solid glasslayer or glaze which corresponds to layer 21 in FIG. 3.

In steps succeeding the step indicated in FIG. 9, another transparentphotographic film 45 is adhered to the upper surface of layer 44, asviewed in FIG. 9. A layer of positive photoresist 46 is then laid on topof film 45. The positive photoresist layer 46 then has portions 47 thatareexposed to light and portions 48 which are not exposed to light.Portions of portions 47 are exposed to light directly, which lightemanates from a lamp 49 and enters plate holes 39, as in FIG. 7.However, in accordance with FIG. 10, portions 47 have a cross sectionlarger than that of holes 39. Moreover, portions 47 have a width andthickness as shown which may be substantially uniform throughout theirentire lengths. Portions 47 may also have lengths substantially longerthan their widths. This is accomplished by a cylinder light reflectinglens raster 50 which has a, more or less, symmetrical axis. Cylinderlens raster 50 may be first held in a position such that its axis liesin a plane of the paper of the drawing of FIG. 10. Cylinder lens raster50 is then moved always in a direction perpendicular to the paper.

As is inherent in positive photoresist, portions 48 harden, and portions47 stay in a condition so that they may be washed away. Portions 47 arethen, in fact, washed away leaving hardened portions 48, shown in FIG.11.

In FIG. 11, a conductive metal layer 51 is then evaporated onto film 45as indicated at 51. Portions of metal layer 51 may build up uponphotoresist portions 48 at 52.

In FIG. 11, film 45 is again shown as a single line. The height ofphotoresist portions 48 has been exaggerated to illustrate the fact thatlayer 51 has a thickness generally very small in comparison to theheight of photoresist portions 48. I

The assembly of FIG. 11 is then fired in a furnace 53, as shown in FIG.12. Again, film 45 decomposes as do photoresist portions 48. This leavesthe structure, as shown in FIG. 12, with insulated and spaced conductivestrips 54 bonded to glass layer 44. Moreover, each strip 54 is insulatedfrom all of the other strips 54, and each strip 54 has a plurality ofholes therein which lie in registration with plate holes 39. Conductivebuildups at 52 are thus dropped off during firing as portions 48decompose, as shown in FIG. 11. The same is true of the portions oflayer 51 which lie in registration with plate holes 39 after film 45decomposes. Strips 54 thus correspond to strips 23, shown in FIGS. 2 and3. A glass layer 55, shown in FIG. 13, is bonded to glass layer 44 andconductive strips 54 by performing the same steps by which glass layer44 was bonded to electrode 33.

Hardened positive photoresist strips 56 are formed on the upper surfaceof glass layer 55 in FIG. 14 in the same manner that portions 48 areformed in FIG. 11.

By the use of strips 56, conductive strips 57 are bonded to glass layer55 in the same manner that strips 54 are bonded to glass layer 44. Thus,glass layer 55 corresponds to glass layer 22, shown in FIG. 3, andstrips 57 correspond to strips 24, shown in FIG. 3.

The section of FIG. 15 does not look like the section of FIG. 3 becausethese two sections have been taken at angles with respect to each otherto show clearly the construction of the finished product. It will benoted that a section taken along the line A-A in FIG. 15 will beidentical to that shown in FIG. 3, and that a section taken along theline B-B in FIG. 3 will be identical to that shown in FIG. 15.

If desired, the steps illustrated in FIGS. l0, l1, l4 and 15 may beperformed without the use of film 45, as shown in FIGS. 16 and 17,respectively. For example, in FIG. 16, parts 32', 33', 34, 44, 47 and48' respectively correspond to parts 32, 33, 34, 44, 47 and 48 in FIG.10.

In FIG. 17, parts 32, 33', 34, 44, 48, 51 and 52' correspondrespectively to parts 32, 33, 34, 44, 48, 51 and 52 shown in FIG. 11.However, layer 51 has holes 58 therein. In FIG. 11, layer 51 does nothave holes therein except where the upper surface of layer 44 is maskedby photoresist portions 48.

The assembly of FIG. 17 is then fired as in FIG. 12. The result is thenthe same as that shown in FIG. 12.

In FIG. 14, the exposed portion of the photoresist, not shown, may beexposed by use of a cylinder lens raster 50' which is moved in thedirection indicated by arrow 50".

Alternatively, cylinder lens raster 50, shown in FIG. 14, may be of aconstruction the same as or similar to that shown in FIG. 10. Cylinderlens raster 50' is, more or less, a group of bodies similar to or thesame as cylinder lens raster 50.

If desired, film 35 and film 45 both may be made of entirelyconventional transparent photographic film.

Whenever either the negative photoresist or the posi- I tive photoresistis exposed to light as in, for example, FIGS. 7, 10, 14 and 16, lamps37, 49, 50" and 50"" may be positioned a substantial distance away fromthe structure illuminated. Moreover, a conventional parabolic reflectormay be provided for each lamp, if desired, for collimation.

A cylinder lens raster 50" identical to cylinder lens raster 50 in FIG.is also shown in FIG. 16.

In FIG. 2, it will be noted that, as stated previously, holes extend allthe way through MCA. 15. The holes may be described as being in columnsand rows. For example, all of the holes in one strip 24 may be describedas a column of holes. All the holes in one strip 23 may be described asa row of holes.

In FIG. 1 1, photoresist strips 48 are thus located midway between twoimmediately adjacent rows of holes in the MCA. The same is true ofphotoresist strips 48, shown in FIG. 17. Strips 56, shown in FIG. 14,are located midway between two immediately adjacent columns of holes.

As stated previously, the drawings are not to scale. Thus, if the sourceof light for photoresist exposure provides collimated light, is spaced asubstantial distance from the photoresist, and provides a light beamwhich, in cross section, is at least as large as the structure beingilluminated or can be moved thereover, light can enter each MCA' hole.However, due to the fact that the lengths of the MCA holes may be muchgreater than the diameters, little light divergence at the far end of ahole will occur. Accurate formations of holes in the laminates is thuspossible.

In accordance with the foregoing, from FIGS. 16 and 17, it will beappreciated that all the conductive strips may beformed in their propershapes, sizes and locations without the use of a film. However, the useof a film or an equivalent thereof is required to support, for example,the exposed portions 40 of the negative photoresist layer 36 afterphotoresist layer portions41 have been washed away. Note that thehardened photoresist layer portions 40 overlie the plate holes 39 inFIG. 7 and are not easily supported except by a film or its equivalent.

The methods of the present invention are by no means limited to makingan MCA of any specific relative or absolute dimensions. However, sometypical dimensions are given in the following.

In the first place, if desired, strips 23 may be three holes wideinstead of one hole wide. However, for strips one hole wide, the spacebetween two immediately adjacent strips 24 may be 1.6 mils. The spacingof strips 24 and and strips 23 may be uniform. The spacing of strips 23may be identical to the spacing of strips 24, if desired. Each strip 24may be 6.0 mils wide. Each strip 23 may have the same width.

Each strip may be centrally located over its corre' sponding column orrow of holes. Each hole may have a diameter of 5.0 mils.

The spacing between the center of the holes in one strip 23 to thecenter of the holes, in a strip immediately adjacent thereto may be 7.6mils. The spacing between the center of the holes in one strip 24 to thecenter of the holes in another strip 24 immediately adjacent thereto mayalso be 7.6 mils.

I An outstanding feature of the MCA 15, shown in FIG. 2, is that strips23 and 24 act in a manner similar to the control grid of a triode andrequire only very small gating voltages.

In FIG. 1, photocathode 14 is maintained at a potential of 0 volts,voltages of O and -3 volts for all of the strips 23 and for all of thestrips 24 are entirely adequate.

Note will be taken that MCA 15, shown in FIG. 2, if fabricated inaccordance with the methods of the pres ent invention, may be used inany of the several embodiments disclosed in the said patent.

By itself, photoresist is well known in the art. However, to make itclear again how the photoresist layers are employed to mask certainsurface portions of the laminate under construction, negativephotoresist hardens when exposed to light. The unexposed portions ofnegative photoresist may thus be washed away. Conversely, the unexposedportions of positive photoresist harden, and the exposed portions ofpositive photoresist may be washed away. I The photoresist layersdisclosed herein preferably have a thickness of about 1.0 mil orgreater. This compares with a thickness of dielectric plate 32 in FIG.15 of, for example, 50 mils.

If desired, films 35 and 45 may be identical. In such a case, each may,if desired, have a thickness of from about 1.0 micron to about 5.0microns. The same is true of strips 23 and 24, and electrodes 19 and 20.

Strips 54 have a thickness much smaller than that shown in FIG. 13.Hence, the use of a film over the top of strips 54 informing glass layer55 thereon does not pose any problem to bonding glass layer 55 to strips54 or to glass layer 44. Glass layer 55 is at least semifluid duringfiring; and during firing, the film is decomposed.

This means that the frit can flow down between conductive strips 54 tobond to glass layer 44. Glass layer 55 will easily bond to conductivestrips 54 in any event.

What is claimed is:

l. The method of fabricating a laminated electron tube structure, saidmethod comprising the steps of: forminga base plate having approximatelyflat opposite side surfaces and having a plurality of holes extendingcompletely therethrough in a directionapproximately normal to said basesurfaces; fixing one side of a transparent film to the surface of oneside of said base to cover said surface and holes; forming a photoresistlayer on the other film side over said surface and holes; directinglight from a position on the other side of said base through said baseholesto expose the areas of said photoresist layer over said holes whilethe other areas of said photoresist layer remain unexposed; washing awaythe unexposed areas of said photoresist layer; and

forming an added dielectric layer on said film over said areas wheresaid photoresist layer was washed away, said exposed layer areas servingto mask a corresponding portion of said other film side; and heatingsaid base, said film and said exposed photoresist layer areas to atemperature causing said film and said exposed photoresist layer areasto decompose leaving said added dielectric layer bonded to said basesurface over the areas substantially congruent with said unexposedareasof said photoresist layer.

2. The method of claim 1, wherein saidphotoresist layer includes anegative photoresist, said added layer being frit, said heating stepbeing performed to raise the temperature of said frit sufficiently highto form a glaze and remove said exposed areas and film.

3. The invention as defined in claim 2, wherein a further transparentfilm layer is fixed to said one side of said base over said glazed fritand holes and a positive photoresist layer is formed on said furthertransparent layer, said positive photoresist layer being exposed tolight in an increased cross sectional area over and extending around andbeyond said holes approximately normal to the axes of said holes, saidincreased area being produced by directing light from said other side ofsaid base through said holes and layers and positioning light reflectinglens means over said positive photoresist layer.

4. The invention as defined in claim 3, including washing away saidincreased area photoresist layer around said holes and depositing anadded conductive metal layer onto said further transparent film in saidincreased area and over the remaining photoresist portion.

5. The invention as defined in claim 4, wherein said added layer has athickness substantially less than that of said remaining photoresistlayer portion.

6. The invention as defined in claim 5, including heating said base,glaze, further transparent film, positive photoresist and metal layersto decompose said film and photoresist and cause said metal layer onsaid film over said holes and remaining photoresist to break off fromsaid base and to leave said holes open and said metal bonded to saidbase in positions around said holes and spaced apart from said metalaround adjacent holes.

7. The invention as defined in claim 6, including forming a furtherdielectric layer over said metal layer and between said holes, andforming conductive electrode strips over said further dielectric layer.

l l =l

2. The method of claim 1, wherein said photoresist layer includes anegative photoresist, said added layer being frit, said heating stepbeing performed to raise the temperature of said frit sufficiently highto form a glaze and remove said exposed areas and film.
 3. The inventionas defined in claim 2, wherein a further transparent film layer is fixedto said one side of said base over said glazed frit and holes and apositive photoresist layer is formed on said further transparent layer,said positive photoresist layer being exposed to light in an increasedcross sectional area over and extending around and beyond said holesapproximately normal to the axes of said holes, said increased areabeing produced by directing light from said other side of said basethrough said holes and layers and positioning light reflecting lensmeans over said positive photoresist layer.
 4. The invention as definedin claim 3, including washing away said increased area photoresist layeraround said holes and depositing an added conductive metal layer ontosaid further transparent film in said increased area and over theremaining photoresist portion.
 5. The invention as defined in claim 4,wherein said added layer has a thickness substantially less than that ofsaid remaining photoresist layer portion.
 6. The invention as defined inclaim 5, including heating said base, glaze, further transparent film,positive photoresist and metal layers to decompose said film andphotoresist and cause said metal layer on said film over said holes andremaining photoresist to break off from said base and to leave saidholes open and said metal bonded to said base in positions around saidholes and spaced apart from said metal around adjacent holes.
 7. Theinvention as defined in claim 6, including forming a further dielectriclayer over said metal layer and between said holes, and formingconductive electrode strips over said further dielectric layer.